The hCLRN1N48K missense mutation is the most common Usher syndrome type III (USH3) causative mutation in North America and among those of Ashkenazi Jewish descent. A high incidence of inherited deaf-blindness in the Ashkenazi Jewish population can be attributed to the hCLRN1N48K mutation. For example, 40% of a cohort of 40 Jews with USH carried the hCLRN1N48K genotype. Despite a high incidence in the Ashkenazi Jewish population, USH3 is a rare disorder. No therapeutic options are available to prevent hearing or vision loss in hCLRN1N48K and devices such as cochlear implants and hearing aids have limitations.
There is no treatment for the eye disorder associated with USH3. USH3 patients having the hCLRN1N48K mutation are typically born with normal hearing and develop hearing loss in their teenage years. They learn to speak normally before their hearing declines and by middle age they are usually deaf. There is a window of opportunity to prevent deafness in hCLRN1N48K patients after early diagnoses and individuals at risk of developing the disease, based on DNA analysis or family history.